I guess the question here is if his moms side's potential "pickyness" overpowered his dads voraciousness. If he inherited coastal eating habits then all you have to do is present him with a rat. If hes picky i would try defrosting your rats alongside a mouse and scenting them that way. I just switched over my coastal from mouse hoppers to rat pups last week, no questions asked. Keep your fingers crossed and hope for the best.